Railroad car draft gear having a long travel

ABSTRACT

A friction/elastomeric pad draft gear to cushion and absorb impacting forces on a railroad car coupler system. The friction/elastomeric pad draft gear includes a housing with a closed end and an open opposite end with a major axis extending therebetween. The open opposite end is provided with inwardly tapered extended internal friction surfaces. A wedge is mounted for axial movement in the open end of said housing and friction devices are positioned within the housing between the wedge and the extended internal friction surfaces. A spring seat is positioned adjacent the friction devices and on top of the elastomeric pad stack. The friction devices engagement with the wedge: forms a first selected angle of about 35 degrees ±3 degrees; forms a second selected angle of about 2.25 degrees, ± about 0.25 degrees, with the extended tapered internal friction surface; and forms a third selected angle of about 90 degrees, ±4 degrees, with the spring seat, all in respect to the major axis.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to draft gears and, in particular, to an improved friction/elastomeric pad draft gear having an extended travel for the absorption and dissipation of input forces.

[0003] 2. Prior Art

[0004] Coupler systems for modern railroad cars typically have included a draft gear assembly to cushion and absorb forces placed on the system during car operation. Devices to cushion and absorb such forces may comprise an elastomeric spring package coupled with a frictional restraint device.

[0005] Examples of such devices are exemplified by U.S. Pat. Nos. 4,556,149 and 4,591,059 both of which are assigned to the assignee of the present invention and incorporated by reference herein.

[0006] While such draft gear devices have high shock absorbing capacities they tend to transmit a high magnitude of force to the car structure during a work cycle.

SUMMARY OF THE INVENTION

[0007] The present invention overcomes the disabilities of the prior art by providing a friction/elastomeric pad draft gear which absorbs energy over a longer distance of travel than prior art devices thereby enabling the transmission of lower levels of force to the rail car structure when cushioning a given energy input. In accordance with friction/elastomeric pad draft gears, the present invention includes a housing with a closed end and an open opposite end which is provided with an extended tapered internal friction surface. A wedge is mounted for axial movement in the open end of the housing and is situated for direct application of draft or buff forces. Friction devices or stepped friction shoes are positioned within the housing, between the wedge and the extended tapered internal friction surface to absorb some of the shock created by the application of a force to the wedge. A spring seat is positioned between the friction devices and the elastomeric pad stack. The stepped friction shoes cooperate with the spring seat to increase the available space for the elastomeric pad stack. A guide spike is secured to the closed end of the housing and passes through the elastomeric pad stack, spring seat and wedge to lessen the potential of buckling of the pad column.

[0008] The friction devices of this invention include a series of annularly spaced friction shoes each having a first, flat beveled inner surface in engagement with a flat beveled inner surface of the wedge. The beveled inner surfaces are formed at a first selected angle with respect to the major axis of the housing. Each of the friction shoes also has a second flat, beveled outer face in engagement with the extended tapered internal friction surface, located in the open end of the housing, forming a second selected angle with the major axis of the housing. Each of the friction shoes also has a third flat, inner face in engagement with a flat, outer face formed in the spring seat, the third flat inner face of the shoe and the outer face of the spring seat being formed at a third selected angle with respect to the major axis of the housing. The guide spike is held stationary at all times as a result of the head of the spike being kept tight against the rear wall of the housing by virtue of the preload to which the elastomeric pad is subjected. A pilot hole through the center of the spring seat and through the center of the wedge enables inward displacement of the wedge and spring seat while maintaining the spike's central alignment.

[0009] In the preferred embodiment of the invention, the first selected angle of the adjoining surfaces of the friction shoe and the wedge is approximately 35 degrees plus or minus about 3 degrees. The second selected angle of the adjoining surfaces of the friction shoe and the extended tapered internal friction surface is approximately 2.25 degrees plus or minus about 0.25 degrees. The third selected angle of the adjoining surfaces of the friction shoe and the spring seat surface is approximately 90 degrees plus or minus about 4 degrees. The elastomeric pad stack comprises a plurality of concentric springs which are made in accordance with U.S. Pat. Nos. 4,198,037 and 4,566,678 which are incorporated by reference herein.

[0010] Thus, an object of this invention is the provision of a draft gear wherein the available travel to installed length ratio is about 0.21. The ratio of the available travel to the installed length of modern draft gears has heretofore ranged from about 0.11 to about 0.16 with the vast majority having a ratio of about 0.14.

[0011] Still a further object of the invention is to provide a draft gear which employs friction/elastomeric devices, fits in a standard pocket, and has 120 mm of travel. This extent of travel having been possible heretofore only with expensive hydraulic draft gears.

[0012] An additional, object of this invention is to provide a draft gear for application in a standard pocket which has 120 mm of travel, weighs less and can absorb more energy than a conventional draft gear.

[0013] Another object of this invention is to provide a stepped friction shoe in combination with a spring seat whereby allowing a longer elastomeric spring column to be located within the draft gear housing.

DESCRIPTION OF THE DRAWINGS

[0014] Other features and advantages of the invention will become apparent in the following description of the preferred embodiment taken in conjunction with the drawings, in which:

[0015]FIG. 1 is a longitudinal cross-sectional illustration of a draft gear according to the invention,

[0016]FIG. 2 is a front elevation view of the draft gear assembly of FIG. 1,

[0017]FIG. 3 is a plan view of the inner or inside surface of a friction shoe for the draft gear assembly of FIG. 1;

[0018]FIG. 4 is a cross sectional view as seen generally along line 4-4 of FIG. 3;

[0019]FIG. 5 is a back end elevational view of the friction shoe of FIG. 3;

[0020]FIG. 6 is a front end elevational view of the friction shoe of FIG. 3;

[0021]FIG. 7 is a side elevational view of the friction shoe of FIG. 3

[0022]FIG. 8 is a outer elevational view of the spring seat for the draft gear assembly of FIG. 1;

[0023] FIG.9 is a cross sectional view as seen generally along line 9-9 of FIG.8;

[0024]FIG. 10 is a front end elevational view of the guide spike of the draft gear assembly of FIG. 1;

[0025]FIG. 11 is a diagram showing force vs. draft gear stroke on a conventional draft gear and on a draft gear which is the subject of this invention, for the same energy input.

[0026]FIG. 12 is an inside elevational illustration of the wedge shown in FIG. 2; and

[0027]FIG. 13 is a outside elevational illustration of the wedge shown in FIG. 12.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0028] As illustrated in the drawings, a friction/elastomeric pad draft gear 9 according to the invention includes an axially bored housing or casing 10 with one end thereof being closed by a fixed enlarged end wall or plate 12. The housing 10 is provided adjacent its open end with a thick-walled friction shell section 14 having three extended tapered internal friction surfaces converging toward the closed end of the housing 10 extended tapered internal friction surface 28 being representative thereof. Spaced inwardly of the shell section 14, the housing 10 is provided with an internal bore 18 which terminates at the end wall 12 and which is characterized by a thinner wall section and by a generally cylindrical inner configuration. The shell section 14 and the bore 18 are integrally interconnected by a transition wall section 20 which serves to blend the configuration of the shell section 14 and the bore 18 into each other both internally and externally.

[0029] As is conventional, a series of three friction shoes 22, 24 and 26 are circumferentially spaced as shown in FIG. 2 in the shell section 14 in sliding friction producing engagement with associated extended tapered internal friction surfaces 28, 30 and 32 of the shell section 14. The three friction shoes 22, 24 and 26 when assembled as shown, define an outwardly opening pocket for receiving the inner end 35 of a wedge 34.

[0030] In addition to the resistance developed in the shell section 14 during inward movement of the friction shoes 22, 24 and 26 and the wedge 34, an elastomeric pad stack 36 comprised of a resilient material is provided in the internal bore 18 of the housing 10. Such resilient material, because it was precompressed during assembly, maintains the wedge and friction shoes in operative engagement with each other and with the housing, both during the operation of the draft gear, as well as during periods of non-operation. The resilient material also resists inward movement of the friction shoes 22, 24 and 26 to cushion some of the draft forces applied to the draft gear

[0031] To retain the wedge 34 and the friction shoes 22, 24 and 26 in the open end 50 of the housing 10, the inner edge 35 of the wedge 34 is provided with a series of circumferentially spaced outwardly projecting flanges 38, 40 and 42 and the housing 10 is provided with a corresponding number of spaced, inwardly projecting lugs 44, 46 and 48 at its open end 50. During assembly of the draft gear the wedge flanges are engaged behind or inwardly of the housing lugs so the wedge 34 and the friction shoes are positively retained in assembled relationship in the housing 10 due also in part to the forces generated by the preload to which the elastomeric pad stack 36 is subject.

[0032] The elastomeric pad stack 36 of resilient material is a series of concentric springs such as 52, each having a center hole such as 53, the last of which is seated against the inner face of the end wall 12. The individual pads are stacked such that the pilot holes in each pad line up to provide a single center pilot hole through the entire pad stack. Further, each individual pad is provided with a metal plate 37 on both the top and bottom surfaces as shown in FIG. 1. As will be more fully explained, the metal plate 39 aids in securing the guide spike 62 while the metal plate 41 abuts the heel portion 73 of each friction shoe. In a preferred embodiment, the elastomeric pad stack is manufactured in accordance with U.S. Pat. Nos. 4,198,037 and 4,566,678, although other suitable resilient material could be used.

[0033] A generally flat symmetrically contoured spring seat 54 is disposed between the outer end 56 of the elastomeric pad stack 36 and the inner end 70 of the friction shoes 22, 24 and 26, and is adapted for longitudinal movement in the housing 10 to compress the stack 36, when force is applied to the wedge 34. The center hole 60 in the spring seat 54, accommodates and stabilizes the guide spike 62 and allows for the spring seat's movement during a work cycle. As shown in FIG. 8 the spring seat 54 includes first, second and third flat, outer faces 64, 66 and 68. First outer face 64, for example, which cooperates with the third flat, inner face 70, of friction shoe 22, as shown in FIG. 1, to form a third selected angle of about 90 degrees plus or minus 4 degrees with respect to the major axis 88 of the draft gear 9. Although not shown, each of the flat outer faces 66 and 68 cooperate with the flat inner faces of friction shoes 24 and 26 (not shown). As seen in FIG. 1 the spring seat 54 fits into a recess 71 created in the bottom portion 73 of the friction shoe 22. Although not shown, each friction shoe 24 and 26 also have such a recess or step in the bottom or heel portion. This arrangement provides more space in the internal transition section 20 and bore section 18 for additional elastomeric pad material and thus allows a more elastic spring column having greater energy absorption.

[0034] Each of the friction shoes 22, 24 and 26 are the same in size, shape and function and thus discussion will be limited to friction shoe 22 with the understanding that it applies as well to friction shoes 24 and 26. In other words, friction shoes 24 and 26 include flat inner faces corresponding to face 70, recess or steps 71 and heel portions 73, etc. The friction shoe 22 includes a first flat, beveled inner surface 82, a second flat, beveled outer face 84 and a third flat, inner face 70.

[0035] The wedge 34 has a series of flat inner surfaces 76, 78 and 80 all of which are the same in size, shape and function and thus discussion will be limited to flat inner surface 76 as seen in FIG. 1 with the understanding it applies in full to flat inner surfaces 78 and 80. The flat inner surface 76 engages the first flat, beveled inner surface 82 of the friction 22 forming a first select angle of about 35 degrees plus of minus 3 degrees with the major axis 88 of the draft gear 9.

[0036] As previously discussed the thick-walled friction shell section 14 has three extended tapered internal friction surfaces all being of the same in size, shape and function and thus discussion will be limited to extended tapered internal friction surface 28 with the understanding that it applies to the other two as well. The extended tapered internal friction surface 28 engages the second flat, beveled outer face 84 forming a second selected angle of about 2.25 degrees plus of minus 0.25 degrees with the major axis 88 of the draft gear 9. In order to achieve extra long travel, the extended tapered internal friction surface 28 is about 5.5 inches or 140 mms in length as from the housing end 50 to the end of the taper at 51.

[0037] The guide spike 62 is held stationary at all times by virtue of the head portion 86 thereof being compressed tight against the end wall 12 by the fact that the elastomeric pad stack 36 has a preload. During a work cycle the pilot hole 53 of the elastomeric pad stack 36, the center hole 60 of the spring seat 54 and center bore 72 of the wedge 34 move relative to the spike 62, enabling inward displacement of the wedge 34 and spring seat 54. The guide spike 62 is sized to be approximately 0.25 inches shorter than the inside length of the housing to allow the follower block (not shown) to butt against the end 50 of the draft gear at full travel, without damaging the spike 62.

[0038] The draft gear 9 described and illustrated herein also has a working stroke of about 116 mm to about 120 mm. The working stroke is the amount of travel of the gear 9 and is the distance the outer face 33 of wedge 34 moves with respect to the open end 50 during a work cycle.

[0039] A further characteristic of the draft gear 9 is the available travel to installed length ratio. This term is the working stroke divided by the distance from the outer face 33 of wedge 34 to the outer surface 39 of the end platel2. As an approximation, dividing about 118 mm by the distance from the outer face 33 to the outer surface 39 which is approximately 568.4 mm results in an available travel to installed length ratio of about 0.21.

[0040] Still a further characteristic of the draft gear of this invention is its ability to cushion an impact and transmit a low level of force in doing so. It can be seen from FIG. 11 that when a mass having kinetic energy strikes a conventional elastomer/friction draft gear, a certain force/travel relationship 101 results. When that same mass, having the same kinetic energy, strikes the draft gear described herein, the resulting force/travel relationship 103 is characterized by a generally lower level of force, that is, spread over a greater range of travel. As would be expected, the work done by either draft gear in cushioning the impact of the moving mass is the same and is confirmed by the same total area beneath the upper graph line and the horizontal axis for either force/travel relationship. By taking advantage of a greater working stroke, the draft gear of this invention can transmit less force to the car structure while dissipating the same energy.

[0041] While embodiments of this invention have been shown and described, it should be understood that this invention is not limited hereto except by the scope of the claims. Various modifications and changes may be made without departing from the scope and spirit of the invention as the same will be understood by those skilled in the art. 

I claim:
 1. In a friction/elastomeric draft gear having a housing with a closed end and an open opposite end and a major axis extending therebetween, said open opposite end being provided with inwardly tapered extended internal friction surfaces, a wedge mounted for axial movement in the open end of said housing and against which a force can be applied, friction devices positioned within said housing between said wedge and said internal friction surfaces and engageable with said wedge and said internal friction surface to absorb the shock created by the application of a force to said wedge, a spring seat positioned adjacent said friction devices, and an elastomeric pad stack positioned between the closed end of the housing and said spring seat to cause the spring seat to urge said friction devices into engagement with said wedge and said internal friction surface, the improvement comprising: a. said friction device includes a series of annularly spaced friction shoes each having a beveled inner surface in engagement with a beveled inner surface of said wedge, said beveled inner surface of said friction device and inner surface of said wedge forming a first selected angle of about 35 degrees plus or minus about 3 degrees with respect to the major axis of said housing, b. said friction shoes each having a beveled outer surface in engagement with said extended tapered internal friction surfaces, said beveled outer surface and said extended tapered internal friction surface forming a second selected angle of about 2.25 degrees plus or minus about 0.25 degrees with respect to the axis of said housing; c. said friction shoes each having a flat inner surface in engagement with a flat outer face formed in said spring seat, the flat inner surface of said friction shoes and the flat outer face formed in said spring seat forming a third selected angle of about 90 degrees plus or minus about 4 degrees with respect to the axis of said housing.
 2. The friction/elastomeric draft gear according to claim 1 wherein said series of annularly spaced friction shoes each have a heel portion, said heel portions each having a recess.
 3. The friction/elastomeric draft gear according to claim 2 wherein said spring seat fits into said recess.
 4. The friction/elastomeric draft gear according to claim 3 including a guide spike secured to said closed end.
 5. The friction/elastomeric draft gear according to claim 4 wherein said elastomeric pad stack includes a pilot hole, said spring seat includes a center hole and said wedge includes a center bore, said guide spike passing through said pilot hole, said center hole and partially through said center bore.
 6. The friction/elastomeric draft gear according to claim 5 wherein said inwardly tapered extended internal friction surface is about 140 mm in length.
 7. The friction/elastomeric draft gear according to claim 6 wherein said elastomeric pad stack is under a preload.
 8. The friction/elastomeric draft gear according to claim 7 wherein said guide spike is secured to said closed end by said elastomeric pad stack subject to said preload.
 9. The friction/elastomeric draft gear according to claim 8 wherein said heel portions of said friction shoes contacts both said spring seat and said elastomeric pad stack.
 10. In a friction/elastomeric draft gear having a housing with a closed end and an open opposite end and a major axis extending therebetween, said open opposite end being provided with inwardly tapered extended internal friction surfaces, a wedge mounted for axial movement in the open end of said housing and against which a force can be applied, friction devices positioned within said housing between said wedge and said internal friction surfaces and engageable with said wedge and said internal friction surface to absorb the shock created by the application of a force to said wedge, a spring seat positioned adjacent said friction devices, and an elastomeric pad stack positioned between the closed end of the housing and said spring seat to cause the spring seat to urge said friction devices into engagement with said wedge and said internal friction surface, the improvement comprising: a. said friction device includes a series of annularly spaced friction shoes each having a beveled inner surface in engagement with a beveled inner surface of said wedge, said beveled inner surface of said friction device and said beveled inner surface of said wedge forming a first selected angle with respect to the major axis of said housing, b. said friction shoes each having a beveled outer surface in engagement with said extended tapered internal friction surfaces, said beveled outer surface of said friction device and said extended tapered internal friction surface forming a second selected angle with respect to the axis of said housing; c. said friction shoes each having a flat inner surface in engagement with a flat outer face formed in said spring seat, the flat inner surface of said friction shoes and the flat outer face formed in said spring seat forming a third selected angle with respect to the axis of said housing; d. said elastomeric pad stack includes a series of elastomeric pads each having a pilot hole; e. said wedge includes a center bore; f. said friction shoes each including a heel portion, said heel portion having a recess; g. said spring seat includes a center hole; and h. a guide spike secured to said closed end passing through said pilot holes, said center hole and partially through said center bore.
 11. The friction/elastomeric draft gear according to claim 10 wherein said spring seat fits into said recess of said heel portion, said heel portion contacting both said elastomeric pad stack and said spring seat.
 12. The friction/elastomeric draft gear according to claim 11 wherein: a. said first selected angle is about 35 degrees, plus or minus about 3 degrees; b. said second selected angle is about 2.25 degrees, plus or minus abut 0.25 degrees; and c. said third selected angle is about 90 degrees, plus or minus about 4 degrees.
 13. In a friction/elastomeric draft gear having a housing with a closed end having an outer surface and an open opposite end having an outer face and a major axis extending there between, said open opposite end being provided with inwardly tapered extended internal friction surfaces, a wedge mounted for axial movement in the open end of said housing and against which a force can be applied, friction devices positioned within said housing between said wedge and said internal friction surfaces and engageable with said wedge and said internal friction surface to absorb the shock created by the application of a force to said wedge, a spring seat positioned adjacent said friction devices, and an elastomeric pad stack positioned between the closed end of the housing and said spring seat to cause the spring seat to urge said friction devices into engagement with said wedge and said internal friction surface, the improvement comprising: a. said friction device includes a series of annularly spaced friction shoes each having a beveled inner surface in engagement with a beveled inner surface of said wedge, said beveled inner surface of said friction device and said beveled inner surface of said wedge forming a first selected angle with respect to the major axis of said housing, b. said friction shoes each having a beveled outer surface in engagement with said extended tapered internal friction surfaces, said beveled outer surface of said friction device and said extended tapered internal friction surface forming a second selected angle with respect to the axis of said housing; c. said friction shoes each having a flat inner surface in engagement with a flat outer face formed in said spring seat, the flat inner surface of said friction shoes and the flat outer face formed in said spring seat forming a third selected angle with respect to the axis of said housing; and d. a working stroke of about 1 18 mm and an available travel to installed length ratio of about 0.21.
 14. The friction/elastomeric draft gear according to claim 13 wherein: a. said elastomeric pad stack includes a series of elastomeric pads each having a pilot hole; b. said wedge includes a center bore; c. said friction shoes each include a heel portion, said heel portion having a recess; d. said spring seat includes a center hole; and e. a guide spoke secured to said closed end passing through said pilot holes, said center hole, and partially through said center bore.
 15. The friction/elastomeric draft gear according to claim 14 wherein said spring seat fits into said recess of said heel portion, said heel portion contacting both said elastomeric pad stack and said spring seat.
 16. The friction/elastomeric draft gear according to claim 15 wherein:
 1. said first selected angle is about 35 degrees, plus or minus about 3 degrees;
 2. said second selected angle is about 2.25 degrees, plus or minus about 0.25 degrees; and
 3. said third selected angle is about 90 degrees, plus or minus about 4 degrees. 